Report: Fish barrier assessment in Barham River Catchment

Executive Summary

The Corangamite Catchment Management Authority commissioned the present study to:

1) Undertake a desktop review of the current information on seven identified barriers;
2) Undertake field assessments of the barriers
3) Prioritise the barriers in terms of benefits of fish passage
4) Make management recommendations including the steps of rehabilitation based on the prioritisation, knowledge gaps and additional data requirements as well as fishway designs and approximate costs.

The project methodology to meet these objectives included an initial review of existing fish distribution data and reports, a site inspection of each barrier to collect relevant information on the structure and quality of local in-stream habitat. The fish passage prioritisation was then conducted by scoring each barrier against a number of criteria which related to the native fish species present, location in the river system, habitat quality, upstream river length to become available, fish species present and stream flow patterns. Indicative costs for fishways at each site have been included in a table of the prioritised barriers.

It is important for these coast streams that the fishways can operate effectively at low flows where the flexible morphology of the larger migratory fish are not impeded by narrow slots or rock placements. The other important data needed to design the fishway are a detailed knowledge of the weir foundations, substrate, and the flow patterns near the barrier during rising flows and accurate depth readings near the barrier to assess low flow access to fish.

Appendix 2 provides some background on vertical-slot and rock-ramp fishways, together with some guidelines that can help ensure the construction of a successful fishway.

Fish Passage Priorities

The highest priority barriers for fish passage were the redundant gauging weir on the Barham River west branch. A vertical-slot fishway is feasible at this weir option but will be at considerable cost compared to weir removal. It is suggested that the feasibility of removing this weir is investigated as a matter of priority.

Weir removal on Wild Dog Creek at Binawee is also the preferred option. In this case a robust method to restore fish passage is to remove the crossings and replace them with a single span bridge or large embedded culverts without raising water velocities. These options need to be compared against the potential cost of a fishway for greatest cost efficiency.

The two barriers on the Barham River East branch should be undertaken together. The private crossing on at Oldenzaal had similar considerations to the crossing at Binawee. A single span bridge or large embedded culverts would be the preferred option, however, a rock ramp fishway could provide fish passage over the existing structure. A rock ramp fishway has already been attempted at the gauging station on the Barham River East branch but could be easily modified into an effective fish passage device. In this case a refurbished the rock-ramp immediate below the structure could be constructed for a minimal cost.

Fish passage at the two sites on the Gellibrand River is desirable because the fishway design is relatively straightforward and the higher flows allow relatively greater latitude in the design. The upstream habitat available to migratory fish is of high quality. While the Gellibrand River also had higher fish species diversity, the two sites scored more moderately on the priority listing because of the minimal (about 2 km) amount of stream length upstream to Stevenson falls.

The Montrose Road crossing at Anderson Creek was a low fish passage priority, largely due to the relatively low diversity of the fish community and the lower quality of habitat it could provide. This site is also technically more difficult for a fishway due to relatively low flows and a large total head loss. Moreover the pipe culverts provide a poor fish passage option. It is suggested that the Corangamite CMA investigate the feasibility of replacing the road crossing in the future in partnership with the roadway managers.

Lastly, it is important that fishways are built with appropriate biological supervision and post construction assessment. Operations staff should also be trained in on-ground fishway operations. Consequently, follow up fish community surveys compared to baseline data should provide a robust demonstration of the benefits of fish passage restoration.

Download the full Fish Barrier report [PDF 4,265KB]

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